Air purification system

ABSTRACT

A fluid purification system is provided for contaminated fluids such as airontaminated with a wide spectrum of chemical warfare agents which includes two adsorption chambers with adsorption medium suitable for effectively removing chemical warfare agents from a stream of air; a valve selection device adapted for directing a stream of contaminated air to one or the other of the adsorption chambers, for directing a stream of contaminant-free air from the adsorption chamber, for directing a stream of regeneration fluid to one or the other adsorption chambers requiring regeneration and for directing a fluid stream with a concentration of contaminants from a regenerated adsorption chamber; a fluid stream diverter device adapted for diverting a portion of contaminant-free fluid from one or the other adsorption chambers for use as a regeneration fluid stream for regeneration of the adsorption medium in one or the other adsorption chambers; and a temperature regulation device for heating the regeneration fluid stream to a temperature effective for regeneration of the adsorption medium in the adsorption chambers.

GOVERNMENTAL INTEREST

The Government has rights in this invention pursuant to Contract No.DAAK-11-81-C-0028 awarded by Department of the Army.

This application is a continuation of application Ser. No. 07/706,422,filed May 28, 1991, now abandoned.

FIELD OF THE INVENTION

The present invention relates to fluid purification systems and, moreparticularly, to mobile purification systems employing adsorbents forremoving a broad spectrum of toxic and noxious contaminants includingchemical warfare agents from contaminated fluid streams such as air inprotected enclosures, armored vehicles and the like, the purificationsystem having means for regeneration of the adsorption medium in situwithout shutting down the purification system.

BACKGROUND OF THE INVENTION

There are many different techniques used to achieve the desiredseparation of contaminants from air and other fluid streams. When thecontaminant concentration is not large in comparison to the bulk stream,two techniques, adsorption and absorption are generally effective. Onoccasion, additional components are added to adsorbents to enhance thebenefits of physical adsorption by utilizing chemisorption. However,utilizing either an absorbent agent or an adsorbent agent with addedchemisorption components results in a purification system that is notreadily regenerable, whereas utilizing physical adsorption alone allowsfor the regeneration of the adsorption agents, in general, either bypressure or temperature variation techniques. The weight and complexityof many regeneration systems, in general, limits their feasibility foruse in mobile applications.

One area where adequate purification of a fluid stream has life anddeath consequences is in the defense against chemical warfare agents. Inthe past, specially treated activated charcoal adsorption medium havebeen developed capable of adsorbing a broad spectrum of chemical warfareagents ranging from low molecular weight agents such as hydrogen cyanideand cyanogen chloride to high molecular weight (nerve agents) agentssuch as soman and sarin and very large agents such as "BZ" and "VX".

The present state-of-the-art for Chemical Defense Collective Protectionfor enclosures, armored vehicles and the like utilizes such speciallytreated activated charcoal adsorption medium in filters and the likedevices, but they have been found to exhibit many drawbacks. The filtershave limited shelf life, are readily fouled by a variety of nontoxiccontaminants such as water and various hydrocarbon vapors, requirefrequent replacement and they cannot be regenerated, necessitatingreplacement, typically, while the protective system is shut down.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a fluidpurification system for use in personnel protection enclosures, armoredvehicles and the like that utilizes adsorption medium suitable toeffectively remove a broad spectrum of chemical warfare agents fromstreams of air wherein the adsorption medium can be regenerated whilethe air purification system is maintained in service.

It is another object of the present invention to provide a mobile airpurification system for use in protected enclosures, armored vehiclesand the like which includes an adsorption medium that would effectivelyremove a broad spectrum of chemical warfare agents from a stream of airand the like, and wherein the adsorption system could be regenerated insitu without the need for replacement of the adsorption medium orshutting down operation of the air purification system.

It is a further object of the present invention to provide a process forpurification of streams of air contaminated with chemical warfare agentsin personnel protection enclosures, armored vehicles and the like whicheffects the purification of streams of contaminated air and regenerationof the air purification adsorption medium without the need to remove orreplace such medium or to shut down the air purification system whileregenerating the adsorption medium.

In accordance with the present invention there is provided a process forthe purification of a stream of contaminated fluid such as aircontaminated with a broad spectrum of chemical warfare agents whichcomprises:

a) providing a first adsorption medium means for adsorption ofcontaminants in a contaminated stream of fluid and a second adsorptionmedium means associated with said first adsorption medium means foradsorption of contaminants in said contaminated stream of fluid;

b) treating a stream of contaminated fluid with said first adsorptionmedium means for the time needed to form a stream of substantiallycontaminant-free fluid;

c) discharging said stream of contaminant-free fluid exiting from saidfirst adsorption medium means after diverting a portion of said streamof said contaminant-free fluid to provide a regeneration fluid stream;

d) heating said diverted regeneration fluid stream to a temperature highenough to desorb contaminants adsorbed by said second adsorption mediummeans from a contaminated fluid stream treated thereby;

e) treating said second adsorption medium means containing contaminantsadsorbed from a stream of contaminated fluid with said heatedregeneration fluid stream for the time necessary to regenerate saidsecond adsorption medium means by desorbing and flushing contaminantsfrom said second adsorption medium means;

f) discharging said regeneration fluid stream with a concentration ofcontaminants desorbed from said second adsorption medium means;

g) cooling said regenerated second adsorption medium means to atemperature effective for said second adsorption medium means to treat astream of contaminated fluid;

h) treating a stream of contaminated fluid with said second adsorptionmedium means while said associated first adsorption medium means isregenerated using steps c) through g) hereof; and

i) repeating said steps b) through h) until terminated by an operator.

In accordance with another aspect of the present invention there isprovided apparatus for the purification of a stream of contaminatedfluid which comprises:

a) a first adsorption chamber means having adsorption medium means foradsorption of contaminants from a stream of contaminated fluid and asecond adsorption chamber means associated with said first adsorptionchamber means having adsorption medium means for adsorption ofcontaminants from a stream of contaminated fluid;

b) adsorber switching valve means adapted for directing a stream ofcontaminated fluid to one of said first and second adsorption chambermeans, for directing a stream of contaminant-free fluid from one of saidfirst and second adsorption chamber means, for directing a stream ofregeneration fluid to one of said first and second adsorption chambermeans and for directing a stream of fluid with concentrated contaminantsfrom one of said first and second adsorption chamber means;

c) fluid diversion means adapted for diverting a portion of a stream ofcontaminant-free fluid from a bulk of said stream of contaminant-freefluid and directing said diverted stream to a temperature regulationmeans;

d) temperature regulation means for heating a stream of contaminant-freefluid and for directing a stream of heated contaminant-free fluid tosaid adsorber switching means; and

e) temperature regulation means for directing a stream of cooledcontaminant-free fluid to said adsorber switching means.

Other objects, features and advantages will be readily apparent from thefollowing detailed description of preferred embodiments thereof taken inconjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there are shown in theaccompanying drawings embodiments which are presently preferred; itbeing understood that the invention is not intended to be limited to theprecise arrangements and instrumentalities shown.

FIG. 1 is a schematic block flow diagram showing an air purificationsystem with regeneration capabilities according to the invention;

FIG. 2 is a schematic block flow diagram illustrating a preferredarrangement of apparatus for carrying out the air purification andregeneration process of the present invention; and

FIG. 3 is a schematic drawing of the control elements used in the systemand process of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to further and more specific details of the presentinvention and with reference to the drawings, wherein FIG. 1 is shownthe fluid purification system of the invention which may, for example,be used for a variety of mobile applications including protectingmilitary personnel inside protected enclosures, armored vehicles and thelike. The system shown in FIG. 1 includes two adsorption chambers 12 and14; an adsorber switching valve 10 which is adapted to direct a feedstream of contaminated fluid such as air containing chemical warfareagent contaminants to one of the two adsorption chambers 12, 14, acontaminant-free air stream from the adsorption chamber for use and/orfurther processing, a regeneration feed stream of fluid to one of twoadsorption chambers 12, 14 requiring regeneration, and the stream offluid with concentrated contaminants from one of two adsorption chambersbeing regenerated; a flow diversion device 16; a temperature regulationdevice 18; and associated devices and controls. Adsorber switching valve10, which is adapted to direct contaminated and regeneration air feedstreams to one of the two adsorption chambers 12, 14, includes, forexample, two valve housings and associated valve components, a singledrive mechanism, a valve positioning device and associated controls.

In operation according to the practice of the invention, a stream ofcontaminated fluid such as air containing chemical warfare agentcontaminants is continuously fed by way of a suitable blower, pump,compressor or the like to the adsorber switching valve 10. It ispreferential that the contaminated stream be cooled and free of waterdroplets before entering adsorption chambers 12, 14. The contaminatedfluid stream enters one of the valve housings 10a of the switching valve10 and is directed thereby to an adsorption medium in the firstabsorption chamber 12 where the contaminants are removed by adsorption.The contaminant-free fluid stream exits from the adsorption chamber 12to a different valve housing 10b in the switching valve 10 and is thendirected by the switching valve 10 to a flow diversion device 16 whichis adapted to separate the flow of contaminant-free fluid into twostreams.

The flow diversion device 16 contains two piping branches, one or bothof which may contain restriction orifices to adjust pressure drops toprovide the desired flows in each direction; or it may contain a pump orcompressor in one or both piping branches to provide the motive forcefor the fluid through each branch. The first branch in the flowdiversion device 16 conveys a bulk of the contaminant-free fluid out ofthe system where the clean fluid is then available for use. In thesecond branch, a portion of the clean fluid is directed to a temperatureregulation device 18 where the clean fluid is heated by a heat source toserve as a regeneration fluid stream. The hot, clean regeneration fluidstream is then returned to the adsorption switching valve 10 where it isdirected to and through the second adsorption chamber 14 which is in theregenerating mode. The heated regeneration fluid stream serves to desorbcontaminants from the adsorption medium and flush then from the secondadsorption chamber 14. The regeneration fluid stream which is nowconcentrated with contaminants exits from the second adsorption chamber14 to the switching valve 10 where it is directed to the waste streamoutlet of the system. The waste stream with concentrated contaminantsmay be further processed, flared or vented to the atmosphere, dependingon the circumstances.

After regeneration, cooling of the regenerated adsorption chamber 14 andadsorption medium therein is initiated. Initiation of the coolingoperation may be controlled by any one of the following: a timer; thetemperature of the waste stream outlet; or chemical analysis of thewaste stream outlet. The cooling operation is commenced by deactivatingthe temperature regulation device 18 and the regeneration fluid streamflows through the adsorber switching valve 10 and the regeneratedadsorption chamber 14 until the regenerated chamber 14 is cooled to ornear the adsorption operating temperature. It would be evident that thetemperature regulation device 18 may be of the type which could beadapted to assist in cooling the regeneration fluid stream. Aftercooling, the switching valve 10 can then be adapted to allow theregenerated second adsorption chamber 14 to be used for adsorption ofcontaminants from a contaminated stream of fluid while the firstadsorption chamber 12 is regenerated. The process can be repeated asindicated above until it is terminated by the operator.

Referring now to FIGS. 2, there is shown a preferred embodiment of theair purification system in accordance with the invention which can be amobile system used to protect miliary personnel inside protectiveenclosures or armored vehicles. The system includes a regeneration heatexchanger 18a and diverter valve 18b which serve as the temperatureregulation device for the regeneration fluid stream.

In operation of the system shown in FIG. 2, the contaminated stream offluid would be treated as described hereinabove with a bulk of thecontaminant-free stream of fluid produced thereby being discharged foruse and a portion of the contaminant-free stream being used as theregeneration fluid stream. The portion of clean fluid diverted by theflow diversion device 16 as the regeneration fluid is directed to thediverter valve 18b. Diverter valve 18b, which can be any conventionalvalve with temperature sensor controlled, motor drive valve positioningmeans or the like, directs a portion of the regeneration fluid stream tothe regeneration heat exchanger 18a. Another portion of the regenerationfluid stream is directed by valve 18b to by-pass the regeneration heatexchanger 18a, and is used to assist in controlling the temperature ofthe regeneration fluid stream being directed to the adsorber switchingvalve 10 prior to entering the adsorption chamber 14 undergoingregeneration. The upper temperature limit of the regeneration fluidstream used to regenerate the adsorption medium in adsorption chamber 14can vary, generally depending upon the temperature limits of theadsorption medium to be regenerated and the limitations of the heatsource. The maximum temperature limits of the adsorption medium aredependent upon the adsorbent's physical characteristics and by theignition temperature of the adsorbent containing adsorbed contaminants.The heat source for the regeneration heat exchanger 18a may be providedby exhaust gases from an engine, steam, electric heat or any otherauxiliary power unit or heat source.

The adsorption chambers 12 and 14 contain adsorption media of activatedcharcoal although other suitable adsorbents may be clay, zeolite such asmolecular sieves, and the like, or mixtures thereof. Adsorption ofcontaminants such as chemical warfare agents from fluid streams such asair can be effectively achieved at temperatures below ambient.Preferably, adsorption of such chemical warfare agent is efficientlyeffected at temperatures between about 32° F. and 50° F. whicheliminates problems with icing of water. These temperatures may beachieved by cooling the contaminated fluid prior to it entering theprocess. If the ambient temperature of the contaminated fluid is below32° F., additional cooling is not required. Regeneration of theadsorption medium at temperatures above 300° F. to about 400° F. effectsadequate desorption of the chemical warfare agents while not posing anignition hazard to the activated charcoal.

In FIG. 3 is shown a schematic diagram illustrating the temperature andpressure sensors and interrelationship thereof with associated equipmentused to control operation of the air purification and regenerationsystem of the invention shown in FIG. 2. The temperature sensors T1, T2,T3, T4 and T6 are the primary control elements for the process, P2 is adifferential pressure sensor used to determine if there is a blockage ofthe adsorption beds in adsorption chambers 12 and 14. In thisconnection, valve position indicators, VPI, provide the signals to theelectronic controller to remove power for the motor drivers, MD, used toposition the valves in adsorber switching valve 10; Temperature sensorT4 controls the diverter valve 18b, sensor T6 senses the temperature ofthe regeneration feed stream to the heat exchanger 18a, sensor T3 sensesthe temperature of the regeneration fluid stream exiting from theadsorption chamber during the regeneration and cooling cycles.

It would be evident that the fluid purification system herein describedwith particular emphasis on its use for removing chemical warfare agentcontaminants from air, with modifications based on the teaching hereincould be applicable for a various stationary and preferably mobileapplications including purifying natural gas streams, water streams,petrochemical fluid streams and a variety of other such industrial andmilitary applications.

Although the fluid purification system and process of the invention havebeen illustrated in the foregoing detailed description, it should beappreciated that other variations may be made. Accordingly, theinvention is not intended to be limited to the specific embodiments orexamples set forth in the specification, but rather is limited only bythe appended claims.

What is claimed is:
 1. A process for the purification of a stream ofcontaminated fluid which comprises the steps of:a) providing a firstadsorption medium means for adsorption of contaminants in a contaminatedstream of fluid and a second adsorption medium means associated withsaid first adsorption medium means for adsorption of contaminants insaid contaminated stream of fluid; b) treating a stream of contaminatedfluid with said first adsorption medium means for the time needed toform a stream of substantially contaminant-free fluid; c) dischargingsaid stream of contaminant-free fluid exiting from said first adsorptionmedium means after diverting a portion of said stream ofcontaminant-free fluid to provide a regeneration fluid stream; d)heating said diverted regeneration fluid stream to a temperature highenough to desorb contaminants adsorbed by said second adsorption mediummeans from a stream of contaminated fluid treated thereby withoutcausing ignition thereof; e) treating said second adsorption mediummeans containing contaminants adsorbed from a stream of contaminatedfluid with said heated regeneration fluid stream for the time necessaryto regenerate said second adsorption medium means by desorbing andflushing contaminants from said second adsorption medium means; f)discharging said regeneration fluid stream with a concentration ofcontaminants desorbed from said second adsorption medium means; g)cooling said regenerated second adsorption medium means to a temperatureeffective for said second adsorption medium means to treat a stream ofcontaminated fluid; h) treating a stream of contaminated fluid with saidsecond adsorption medium means while said associated first adsorptionmedium means is regenerated using steps c) through g) hereof; and i)repeating said steps b) through h) until terminated by an operator. 2.The process as claimed in claim 1, wherein said stream of contaminatedfluid is a stream of air contaminated with chemical warfare agents. 3.The process as claimed in claim 1, wherein said adsorption medium meansincludes activated charcoal.
 4. The process as claimed in claim 1,wherein said regeneration fluid stream is heated to a temperature atleast 300° F.
 5. The process as claimed in claim 1, wherein saidregenerated second adsorption means is cooled to a temperature at orbelow ambient temperature.
 6. The process as claimed in claim 1, whereintreatment of a stream of contaminated fluid by said first and secondadsorption medium means is carried out at a temperature of from about32° F. and 50° F.
 7. Apparatus for the purification of a stream ofcontaminated fluid which comprises:a) a first adsorption chamber meanshaving adsorption medium means for adsorption of contaminants from astream of contaminated fluid and a second adsorption chamber meansassociated with said first adsorption chamber means having adsorptionmedium means for adsorption of contaminants from a stream ofcontaminated fluid; b) adsorber switching valve means adapted fordirecting a stream of contaminated fluid to one of said first and secondadsorption chamber means, for directing a stream of contaminant-freefluid from one of said first and second adsorption chamber means, fordirecting a stream of heated regeneration fluid to one of said first andsecond adsorption chamber means and for directing a stream of fluid withconcentrated contaminants from one of said first and second adsorptionchamber means; c) fluid diversion means adapted for diverting a portionof a stream of contaminant-free fluid from a bulk of said stream ofcontaminant-free fluid and directing said diverted stream to atemperature regulation means; d) temperature regulation means forheating a stream of contaminant-free fluid and for directing a stream ofheated contaminant-free fluid to said adsorber switching means; and e)temperature regulation means for directing said stream of cooledcontaminant-free fluid to said adsorber switching means.
 8. Theapparatus as claimed in claim 7, wherein said temperature regulationmeans includes heat exchanger means.
 9. The apparatus as claimed inclaim 8, wherein the heat source for said heat exchanger is provided byexhaust gases from a vehicle engine.
 10. The apparatus as claimed inclaim 7, wherein said adsorption medium means includes a bed ofactivated charcoal.